<!-- 
    //设置填充颜色
    ctx.fillStyle = "rgb(200,0,0)";
    //填充到矩形
    ctx.fillRect(10, 10, 55, 50);
 -->
<html>
<head>
    <script type="application/javascript">
        function draw() {
            var canvas = document.getElementById("canvas");
            if (canvas.getContext) {
                var ctx = canvas.getContext("2d");

                ctx.fillStyle = "rgb(200,0,0)";
                ctx.fillRect(10, 10, 55, 50);

                ctx.fillStyle = "rgba(0, 0, 200, 0.5)";
                ctx.fillRect(30, 30, 55, 50);
            }
        }
    </script>
</head>

<body onload="draw();">
    <canvas id="canvas" width="150" height="150"></canvas>
</body>

</html>